The invention relates to an electronic gain-control arrangement, i.e. to a circuit arrangement whose gain can be varied by means of a control voltage. Such a circuit arrangement is known from DE-PS 24 04 331. The arrangement described therein comprises two converter circuits whose high-impedance outputs are each connected to the inputs of a current distribution circuit. Two outputs of the current distribution circuits, whose output currents can be controlled by the control voltage on the control input of the current distribution circuit, have a common resistor through which the output currents flow. The voltage across this resistor is applied to the inputs of the two converter circuits via an amplifier so as to obtain negative feedback, the input signal of the circuit arrangement also being applied to one converter circuit.
In many cases the control characteristic of such a circuit arrangement should be such that the amplitude of the output voltage is related to the control voltage exactly in accordance with an e-function, which is referred to hereinafter as "dB-linear". The known circuit arrangement, however, a dB-linear control characteristic over a very small amplification range and moreover produces comparatively strong even harmonics at its output. The last-mentioned disadvantage is mitigated in the circuit arrangement in accordance with German Patent Application P 30 24 142.0. This arrangement in addition comprises two further current-distribution circuits and two further converter circuits, the phase of the signal applied to the additional current-distribution circuits via the additional converter circuits being opposed to that of the signal applied to the two other current distribution circuits. The output voltage is subtracted. However, this circuit arrangement also has a dB-linear control characteristic over only a comparatively small range.
From U.S. Pat. No. 3,714,462, an electronic gain control arrangement is known which comprises two pnp and two npn-transistors and which has a dB-linear control characteristic over a comparatively large range if the characteristics of these transistors correspond to each other. However, since this requires the use of transistors of opposite conductivity types with matching characteristics, this circuit arrangement cannot readily be constructed in integrated circuit technology.